The preparation of foams requires the use of a number of materials that are hazardous to both the environment and persons who are exposed to these materials. Of further concern are the emissions that are generated when these foams are heated after their preparation, e.g., during the preparation of foam products.
For example, in the preparation of polyurethane foams, the composition from which the foam is prepared includes isocyanates and a variety of other harmful organic components. Therefore, from the time the foam-forming process begins (by depositing the composition onto a substrate), the air about the composition is contaminated with volatile, vaporous organic components. Moreover, and as the foam is being prepared, new compounds produced from the reaction of certain of the foam-forming components will also be released into the air. Further, as the composition completes its rise and reaches a self-sustaining configuration, a smoke will emanate from the foam, further contaminating the surrounding environment.
The generation of that smoke during foam preparation, and its general content, are well known and appreciated by those skilled in the art. The smoke will generally comprise visible vapors and particulate matter up to about 5 microns in average diameter, as well as certain invisible vapors and gases, e.g., toluene diisocyanate, moisture, and carbon dioxide. The precise content of the smoke, of course, as will be readily appreciated, will vary depending upon the particular foam being prepared.
After the foam is fully-formed, it may be further processed to provide a foam product. Examples of such processes that are typically used to provide such products include flame lamination, heat compression, hot wire cutting, heat skinning, and heat lamination. All of these processes require the application of heat to the foam. The application of such heat, however, results in the generation of hazardous emissions which may include carbon monoxide, aldehydes, and hydrocarbons. While the precise composition of such hazardous emissions will, as expected, vary with regard to the particular foam being processed and processing conditions, several are similar to the emissions present in the smoke generated during the preparation of the form. By way of example, in the case of a polyurethane foam, isocyanates and antioxidants would likely be present in emissions generated during both foam preparation and fabrication.
In order to maintain the air quality in the foam production facility during preparation of the foam, the foam production line is typically at least partially enclosed along its top and sides. An exhaust air stream is then drawn over the line to collect the emissions emanating from the foam during its production. This stream of exhaust air is then either discharged into the atmosphere directly or is treated, in order to lower the level of emissions entering the atmosphere.
One method, and related apparatus, that has been proposed for removing, from an exhaust air stream, the fine particulate matter and vapor released during foam preparation is provided by U.S. Pat. No. 5,123,936. More specifically, that method and apparatus are said to provide for the treatment of an exhaust stream which comprises particulate matter and vapor that has been generated during one particular stage of foam preparation, i.e., during the "rapid cooling" of the foam. This rapid cooling procedure is employed at the end of the foam-forming reaction to avoid heat degradation in, and improve uniformity of, the physical properties of the foam. The treatment employs the use of a water spray of fine droplets and a water-wetted mechanical filtration system which function to reduce the level of impurities in the exhaust air stream.
U.S. Pat. No. 5,223,552 provides another method, and related apparatus, for removing particulate matter and vapors generated when accelerating the cooling of a foam after it has completed its rise. This method comprises collecting the emissions generated during that phase of foam production in an exhaust air stream, and then passing that air stream through at least one bed containing activated carbon char or activated charcoal to remove the emissions from the air stream. One problem inherent with this method and apparatus is that the presence of moisture is said to have a deleterious effect upon the operation of the activated bed. Thus, if moisture in that air were to condense, it would have to be removed from the air prior to the introduction of the air stream into the treatment bed.
U.S. Pat. No. 4,966,920 discloses yet another means for reducing the level of contaminants in an air stream. However, this method is directed toward suppressing the formation of smoke and gases which typically emanate from natural or synthetic polymer materials during their combustion (burning). This method is said to be particularly applicable when materials containing isocyanate components are burned, e.g., polyurethane foams. The method itself comprises combining a combustible material containing urethane linkages with, as a smoke and toxic gas suppressant, a particular class of polyester during the manufacture of the foam. These polyesters are said to act alone to suppress the amount of smoke and gas emitted during the combustion of a foam prepared using those polyesters. No other components are required to be added to accomplish this suppression.
In view of the foregoing, it is an object of the present invention to provide a method for reducing the quantity of emissions emanating from foam-forming compositions during the preparation of foams from such compositions.
Another object of the present invention is to provide a method for reducing the quantity of emissions emanating from fully-formed foams during hot processing of such foams.
It is a further object of the present invention that the reduction of those emissions be attained at a relatively low cost.
Yet another object of the present invention is to reduce those emissions using materials that are not harmful to either the persons who work closely with those materials or the environment.
A further object of the present invention is to provide a method for reducing such emissions which is not affected by the presence of moisture in the air in which the emissions are carried.
These and other objects and advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.